Food allergy and atopic dermatitis typically start the ?allergic march? in an infant. According to CDC, food-induced anaphylaxis is the leading cause for anaphylaxis and allergic conditions are among the most common medical conditions affecting children in the United States. Although there is no significant trend in respiratory allergies, they remain the most common type of allergy among children (17.0% in 2009?2011). Allergic diseases and asthma pose significant economic burden and quality of life issues. Heredity is a strong determinant but environmental factors, including a western lifestyle, microbial exposures and diet likely play a role in the rise atopic diseases. Among those, human milk may play a critical role considering that maternal, rather than paternal atopic status has a greater effect on the atopic outcome of progeny. Systematic reviews and meta-analyses have concluded an overall protective effect of breastfeeding against atopic dermatitis, wheezing and cow's milk allergy in early childhood, but the exact mechanism is unknown. Human milk oligosaccharides (HMO) provide the main substrate for infant's gut microbiota, thereby playing a prominent role in driving its diversity. Human observational studies have reported imbalances in gut microbiota composition that precedes the development of atopy and atopic eczema. Additionally, human milk is a rich source of immunostimulatory and regulatory cytokines, some of which have been associated with protection or risk factors for allergies in the infant. Our long-term goal is to understand the role of breast milk in development of anti/pro-allergic immune responses. The overall objective of this application is to expand our understanding of entire milk cytokine and oligosaccharide composition in relation to development of allergic conditions. Our central hypothesis is that breast milk bioactive substances are part of the normal gut maturation process and promote development of neonatal gut microbiome and anti-allergic immune responses, which is altered in allergy. We will assess human milk cytokine composition by multiplex platform including proinflammatory, Th2- and Th17-type cytokines and HMOs by HPLC utilizing two historical cohorts with leftover breast milk samples that followed children for development of allergic diseases. Levels of bioactive substances will be compared between milk from mothers with allergic or non-allergic children utilizing systems biology approach and logistic regression analyses. The rationale for the proposed research is to understand human milk composition to establish the basis for interventional studies to modify its anti-allergic properties.